Device for extracting piles or the like



P. SCHMIDT May 12,, 1970 Filed Nov. 8, 1968 Fig.2

United States Patent M Int. or. am 7/06, 9/00 US. Cl. 173-131 6 Claims ABSTRACT OF THE DISCLOSURE An extractor device for extracting piles, sheet piles, jammed drill rods or like structures of the kind comprising a tension rod for attachment to the structure to be extracted, a crosshead fixed to the top of the tension rod and an impact hammer in the form of an annular piston which surrounds the tension rod and moves upwards and downwards within a cylinder mounted on the tension rod to provide impacts on the crosshead at each upward stroke, is provided with a buffer chamber at the top of the cylinder, the chamber being filled with buffer liquid with which the piston comes into contact at the end of its working stroke so that the impact is applied to the crosshead through the liquid. This provides a cushioning effect which greatly reduces the noise produced by the device.

The invention relates to devices for extracting foundation piles, sheet piles, jammed rock drills and the like, of the kind comprising a tension rod, for attachment to the structure which is to be extracted, a crosshead attached to the tension rod and an impact hammer in the form of a piston which is housed in a cylinder and is capable of moving coaxially relative to the tension rod.

A d vice of this kind, for releasing jammed rock drills is described in German patent specification No. 1,054,- 399. In this device, the tension rod passes through the cylinder the upper end of which is thrust against the crosshead by the action of a compression spring. The cylinder contains an impact hammer in the form of an annular piston which is capable of moving coaxially with respect to the tension rod. At the end of its working stroke the piston strikes the crosshead, transferring impact energy to the crosshead and so to the tension rod, and so ultimately to the stuck rock drill. United States patent specification No. 2,035,156 describes an extraction device in which the jammed rock drill is released by means of an elongated, two-armed stirrup. A plunger actuated by an impact hammer strikes against the upper block of the stirrup. In these known devices the impact hammers can be driven electrically, or by compressed air or other gas, or by hydraulic liquid under pressure. However these known devices have the disadvantage that the transfer of energy from the impact hammer to the crosshead or stirrup produces a noise so violent that it can be intolerable to the operator or to others in the neighbourhood.

The aim of the present invention is to provide a less noisy extraction device and to this end, according to this invention in an extraction device of the kind described we provide a chamber for a buffer liquid between the piston and the crosshead so that, in use, the impact of the piston is transmitted to the crosshead through the buffer liquid at the end of the working stroke of the piston. In

Patented May 12, 1970 ice this way a hydraulic cushion is formed which transmits the impact energy from the piston to the crosshead in a comparatively silent manner. The cushion of liquid transmits the impact energy of the hammer and at the same time absorbs the oscillation energy of the metal parts, particularly the high frequency oscillations which are mainly responsible for the objectionable noise.

In principle it is sufiicient to interpose a hydraulic cushion between the driving surface of the piston and the driven surface of the crosshead. However in view of the high pressures involved it would be necessary to use a very carefully constructed seal between the moving parts in the region of the liquid cushion. In order to avoid this difficulty, the cross section of the chamber is preferably the same as that of the corresponding end surface of the piston so that the piston itself seals off the chamber at the end of its working stroke trapping buffer liquid in the chamber, so that the pressure rise is limited essentially to the interior of the chamber.

Furthermore, in view of the fact that the buffer liquid gradually gets heated by absorbing impact energy, the device is preferably arranged so that the liquid in the buffer chamber is constantly removed and replaced by fresh liquid. This is effected by making the diameter of an axial bore in the piston through which the tension rod extends greater than the diameter of the tension rod so as to connect together the two cylinder spaces situated at the two ends of the piston. Both these spaces contain buffer liquid which is preferably hydraulic oil. When the device is in operation the buffer liquid in the buffer chamber is mixed, at each stroke of the piston, with the liquid situated in the two cylinder spaces and in the bore extending through the piston.

In order to provide a hydraulic cushion at the end of the piston return stroke as well as at the end of the working stroke, there is preferably a second chamber for the buffer liquid at the bottom of the cylinder so that, in use, the impact of the piston is transmitted to the bottom of the cylinder through the buffer liquid at the end of the return stroke of the piston. This second chamber also preferably has a cross section which is the same as that of the corresponding end surface of the piston.

During the working stroke of the piston the crosshead is moved away from the cylinder by a reaction thrust. At the end of the return movement of the crosshead, approaching the cylinder once more, the crosshead tends to collide violently with the end of the cylinder, or with a shoulder of the cylinder. To prevent a metal to metal collision between the crosshead and the cylinder, according to a further feature of the invention, the crosshead extends into a recess in the upper end of the cylinder the recess communicating with the space in the upper end of the cylinder above the piston. As soon as the crosshead and the cylinder move away from each other a second buffer chamber is then formed between the crosshead and a shoulder at the bottom of the recess in the cylinder. The gap or buffer chamber thus formed is immediately filled with buffer liquid, forming a hydraulic cushion which gives an almost silent return movement to the crosshead.

The extraction device in accordance with the invention is preferably driven hydraulically, and for this purpose the piston has a collar separating an upper pressure chamber to which the admission of fluid under pressure drives the piston on its return stroke, from a lower pressure chamber, to which the admission of fluid under pressure drives the piston on its working stroke An example of an extraction device constructed in accordance with the invention is illustrated diagrammatically in the accompanying drawings in which:

FIG. 1 is an axial section through the device showing the piston when it has almost completed its return stroke; and

FIG. 2 is a similar section, but showing the piston when it has just completed its working stroke.

The device comprises a cylinder 1 through which a tension rod 2 passes. On the upper end of the rod 2 a crosshead 3 is mounted. Near its lower end the tension rod 2 has a foot 4 on which a compression spring 5 acts. The other end of the spring 5 seats in the cylinder 1. The lower end of the tension rod 2 terminates in an eye 6 into which, for example, a gripper for extracting a pile can be fixed. The cylinder 1 also contains an annular piston 7 which is capable of moving up and down coaxially with the tension rod 2, the piston 7 forming the impact hammer of the device.

The crosshead 3 is housed in a recess 9 in the top end of the cylinder 1. The lower surface of the crosshead 3 has an annular recess in the form of a buffer chamber 10, the cross section of which corresponds to that of the annular upper end 11 of the piston 7. Buffer liquid, preferably hydraulic oil, fills the inner space consisting of the butter chamber 10, an upper cylinder chamber 12, a bore 13 in the piston 7 and a lower cylinder chamber 14. The crosshead 3 is sealed against the cylinder 1 by a sealing ring 15. The upper end of the crosshead 3 terminates in an eye 16 for suspending the device.

The piston 7 has a collar 17 which separates an upper pressure chamber 18 from a lower pressure chamber 19. In operation, hydraulic liquid under pressure is admitted alternately to the lower pressure chamber 19, for driving the piston 7 upwards on its working stroke, and to the upper pressure chamber 19, for driving the piston 7 downwards again, on its return stroke.

When the parts are in the positions shown in FIG. 1, with the piston moving downwards very near the end of its return stroke, hydraulic liquid under pressure is entering the chamber 18, driving the piston downwards in the direction of the chamber 14. During this movement the butter liquid in the lower chamber 14 flows upwards through the part of the bore 13 which is not occupied by the tension rod 2 and enters the upper chamber 12. At the same time, hydraulic liquid escapes from the lower pressure chamber 19.

As soon as the piston 7 has completed its return stroke, liquid under pressure is admitted into the lower pressure chamber 19, driving the piston 7 upwards. During this upward movement of the piston on its working stroke the buffer liquid contained in the upper chamber 12 flows downwards through the bore 13 into the lower chamber 14, while at the same time liquid is expelled from the upper pressure chamber 18. During the working stroke of the piston, the hydraulic pressure in the lower chamber 19 applies a downward reactive thrust to the cylinder 1, thrusting the cylinder downwards relative to the tension rod 2 and compressing the spring 5. Towards the end of its working stroke the piston 7, having now reached its highest speed of movement, strikes with its upper end surface 11 against the butter liquid in the buffer chamber 10. The piston at the same time seals the chamber off from the upper chamber 12, so that buffer liquid is trapped in the chamber 10. The result is an impact given by the piston to the buffer liquid trapped in the annular chamber 10. The axial component of the impact energy is transferred to the crosshead 3, the radial components being taken by the side walls of the buffer chamber 10. The impact energy received by the crosshead 3 is transferred to the tension rod 2, and from there to the pile or other structure being extracted.

During the working stroke of the piston, the reactive thrust applied by the pressure liquid in the chamber 19 thrusts the cylinder 1 downwards, relative to the tension rod 2 and the crosshead 3, against the influence of the compression spring 5, far enough to open up a gap between a lower annular face 20 of the crosshead 3 and a shoulder 21 of the cylinder housing 1. Buffer liquid flows into this annular gap. However just before the end of its working stroke the piston 7 seals the gap, as shown in FIG. 2. During the return movement of the cylinder 1 the energy stored in the spring 5 is transferred through the buffer liquid to the annular surface 20 and so to the crosshead.

As soon as the piston 7 has completed its working stroke, as shown in FIG. 2, the flow of pressure liquid is reversed, so that liquid once more enters the chamber 18, and the cycle is repeated. In order to ensure that the energy of impact is also absorbed silently at the end of the return stroke of the piston, the bottom of the lower chamber 13 has a buffer recess 22 which cooperates with the corresponding lower end surface 23 of the piston 7, so that here again a buffer cushion of liquid is formed.

The main advantage of the extraction device according to the present invention is that there are no impact surfaces where metal strikes directly against metal. Instead, between the end surfaces of the piston and the corresponding impact surfaces of the crosshead, and of the cylinder, the impacts are taken by bulfering cushions of liquid.

I claim:

1. In an extraction device for extracting piles and like structures of the kind comprising a tension rod, means for attaching said tension rod to said structure to be extracted, a crosshead fixed to said tension rod, a cylinder mounted coaxially on said tension rod below said crosshead and a piston forming an impact hammer reciprocable in said cylinder coaxially with said tension rod, the improvement comprising means defining a buffer chamber between said piston and said crosshead and buffer liquid in said buffer chamber whereby, in use, impact of said piston upon reciprocation thereof through a working stroke is transmitted to said crosshead through said buffer liquid.

2. An extraction device as claimed in claim 1, further comprising means defining a second buffer chamber at the end of said cylinder remote from said crosshead and further buffer liquid in said second buffer chamber, whereby impact of said piston upon reciprocation thereof through a return stroke is transmitted to said bottom of said cylinder through said buffer liquid in said second buffer chamber.

3. A device as claimed in claim 1, wherein said piston includes an end surface at the end thereof adjacent said buffer chamber and said buffer chamber has a cross section the same as that of said end surface whereby said piston seals off said buffer chamber at the end of said working stroke trapping said buffer liquid in said buffer chamber to limit the pressure rise in said buffer liquid consequent upon the impact of said piston thereon essentially to the interior of said buffer chamber.

4. A device as claimed in claim 1, further comprising a collar surrounding said piston, means defining upper and lower pressure chambers in the wall of said cylinder, said collar being reciprocable in said pressure chambers and separating said upper pressure chamber from said lower pressure chamber, and means for the admission of fluid under pressure alternately to said upper pressure chamber and said lower pressure chamber, admission of fluid to said lower pressure chamber driving said piston upwards into impact relation with said buffer liquid in said buffer chamber in a working stroke and admission of fluid under pressure to said upper chamber driving said piston downwards on a return stroke.

5. A device as claimed in claim 1, further comprising means defining an axial bore through said piston, said tension rod extending through said bore and said bore having a greater diameter than said rod.

6. A device as claimed in claim 5, further comprising means defining a recess in the end of said cylinder adjacent said crosshead, said crosshead extending into said recess, wall means of said cylinder and said piston defining a space 6 in the end of said cylinder adjacent said crosshead and 1,566,631 12/1925 Sturtevant 173-91 means communicating said recess With said space. 3,352,143 11/ 1967 Bollar 92-134 X Referen s Cited ERNEST R. PURSER, Primary Examiner UNITED STATES PATENTS 5 1,292,429 1/1'919 Bull 173-91 X 1,310,408 7/1919 Boardman 173-132X 132 

